The invention relates to an electronic device equipped with a touch panel, and method for detecting coordinates.
As is well known, a touch panel is a combination of a display device, like a liquid crystal panel, with a touch pad (a position input device).
Some touch panels are of a capacitive type. The capacitive type touch panel enables performance of manipulation at a height within a predetermined range without contact of a finger with a panel screen (the proximal operation is hereunder called “hover manipulation”). FIG. 10 is a drawing showing a general configuration of the capacitive type touch panel. In the drawing, transmission electrodes 101 and reception electrodes 102 are disposed at a position distant from each other on a bottom surface of a plate-shaped dielectric 100. A drive pulse is applied from a drive buffer 103 to the transmission electrodes 101. An electric field develops when the drive pulse is applied to the transmission electrodes 101. When a hand is put in the electric field, the number of electric lines of force existing between the transmission electrodes 101 and the reception electrodes 102 decreases. A change in the number of electric lines of force appears as a change in electric charges of the reception electrodes 102. An approach of the hand to the touch panel is detected by the change in the electric charges of the reception electrodes 102.
FIGS. 11A to 11C are drawings showing a state of detection of a finger achieved when the hand is gradually brought closer to the touch panel. FIG. 11A shows a state in which the hand stays away from the electric field; FIG. 11B shows a state of detection of a hovering finger achieved when the finger has entered the electric field; and FIG. 11C shows a state of detection of a finger touch achieved when the finger is fully in the electric field and remains in touch with the touch panel.
Incidentally, when the finger touches the touch panel for manipulation purpose, erroneous manipulation does not occur. However; for instance, when the touch panel is manipulated with one hand, a remaining part of the thumb, such as a base of the thumb, may be detected before coordinates for the thumb are detected. Thus, user's intended manipulation may be hindered.
A method for preventing occurrence of user's unintended manipulation is an input control method described in connection with; for instance, Patent Document JP-A-2012-234386. The input control method includes detecting a touch on a touch panel: specifying a zone including at least a touched area as an invalid zone in which input manipulation is not accepted; and performing input processing relevant to a touched area when a touch on the touch panel is detected and when the touched area does not belong to the invalid zone.